authorities are saying that suspect number two dzhokhar tsarnaev is armed and extremely dangerous, may be wearing a suicide vest. >> indications are strong that the current outstanding party may be wearing a suicide vest. again, all units use extreme caution approaching any party that matches the description of the outstanding party. >> reporter: it began last night. with the robbery of a convenience store in cambridge at approximately 7:30. a surveillance camera inside the store, caught the image of the man eye dented mied five hours earlier of suspect number two in the marathon bombings. on the campus of m.i.t. a shoot-out that left an police officer dead. next, the two men carjacked a rcedes and then led the police on a wild, violent chase >> wha reports that have explosives at the scene. >> reporter: two men firing weapons and tossing explosives at the cars of pursuing police. the chase ended a with a gun fight in a residential neighborhood in watertown, where one resident took these pictures showing bullet holes. >> several explosive devices were discharged from the car at the pol